Run the following command to find the remaining dependencies. Be sure to replace vpc-id with your VPC ID and NetworkInterfaceId
aws ec2 describe-network-interfaces --filters 'Name=vpc-id,Values='$vpc | grep NetworkInterfaceId
Assuming you created/deleted this ECS cluster on the console, have you checked if the Cloudformation Stack has successfully removed all resources? As explained here: https://docs.aws.amazon.com/AmazonECS/latest/developerguide/create_cluster.html
The console cluster creation wizard provides a simple way to create the resources that are needed by an Amazon ECS cluster by creating a AWS CloudFormation stack.
Look for all objects that could be associated with the VPC that contains these un-deletable Network Interfaces like Load Balancers, EndPoints, Volumes, RDS db, etc., and delete them.
cannot delete network interfaceasked a year ago
Can't delete network interface despite there is no instance using itasked 10 months ago
Error deleting network interface - no permissionasked 4 years ago
Unable to delete network interfaces attached to VPC Endpointasked a year ago
How can I delete an "in-use" network interface that is no longer actually in-use?asked a year ago
Not able to delete VPCs, Subnets, SGs, and Network Interfacesasked a year ago
Cannot Delete Network Interfaceasked 8 months ago
How long does it takes for ECS network interface to be fully removed?asked 7 months ago
Cannot delete network interface?asked 9 months ago
Unexpected EC2 error while attempting to Create Network Interface UnauthorizedOperation while using boto3asked 10 months ago